In recent years, a water absorbent resin has been widely used in absorbent articles such as a disposable diaper, a sanitary napkin and an incontinent pad, as an absorbent material to absorb body liquid such as urine or blood.
As the water absorbent resin, for example, there have been known a cross-linked product of partially neutralized polyacrylic acid, a hydrolysate of a starch-acrylonitrile graft polymer, a neutralized product of a starch-acrylonitrile graft polymer, a saponified product of a vinyl acetate-acrylate ester copolymer, a cross-linked product of carboxymethylcellulose, a hydrolysate of an acrylonitrile copolymer or an acrylamide copolymer, or a cross-linked product thereof, a cross-linked product of a cationic monomer, a cross-linked isobutylene-maleic acid copolymer, and a cross-linked product of 2-acrylamide-2-methylpropane sulfonic acid and acrylic acid or the like.
It is desirable that the water absorbent resin is superior generally in absorbency, absorption rate in contacting with aqueous liquid such as body liquid, liquid permeability, gel strength of a swollen gel, as well as water absorbing characteristics such as sucking amount to suck up water from a substrate containing aqueous liquid. In addition, it is desirable that the water absorbent resin to be used for, in particular, a diaper or the like, is provided with deodorant function and antimicrobial function, other than such absorbing characteristics. Under these circumstances, various investigations have been performed to furnish deodorant function and antimicrobial function by adding deodorant or antimicrobial agent to the water absorbent resin.
As an attempt to furnish deodorant function and antimicrobial function to the water absorbent resin, there has been proposed a method for adding various deodorants and/or antimicrobial agents in combination. For example, in JP-A-60 (1985)-158861, there is described a water absorbent resin composition (a water absorbing agent) composed of the water absorbent resin and an extract of leaves of a Theaceae plant. In JP-A-11 (1999)-241030, there is described a water absorbent resin composition containing an extract essence of a coniferous tree and the water absorbent resin having specific performance. In U.S. Pat. No. 5,980,879, there is described a deodorant water absorbent resin composition dispersed with zeolite particles inside the water absorbent resin. In JP-A-12 (2000)-051339, there is described a persistent antimicrobial deodorant provided with a powder of at least one kind of an extract of horseradish, an extract of mustard, or allyl isothiocyanate, and a water absorbent gelling agent as a persistent agent to maintain antimicrobial and deodorant action of said powder. In WO00/001479, there is described a powder-like water absorbent resin composition, having deodorant property and antimicrobial property, composed of the water absorbent resin, a compound having antimicrobial function against an ammonia-producing bacteria, and a drug having neutralization capability or the neutralization capability and adsorption capability against ammonia. In US-A-2001/0053807, there is described a water absorbent resin composition etc. containing a water-soluble deodorant in a specific water absorbent resin.
In addition, there have been performed also attempts to furnish deodorant function to the absorbent articles used the water absorbent resin. For example, in JP-A-02 (1990)-041155, there are described absorbent articles containing a tea product and a water absorbent resin. In JP-A-63 (1988)-135501, there is described a disposable diaper containing a resin having benzalkonium chloride and/or chlorhexidine gluconate in a water absorbent resin.
Further, there have been reported various attempts other than the above. For example, in JP-A-04 (1992)-139104, there is described a gel-like pesticide obtained by making absorbed aqueous emulsion having a volatile monoterpene-based compound as a main component, into a water absorbent resin. In JP-A-03 (1991)-059075, there is described a production method for an antimicrobial resin composition provided with an antimicrobial coating film at the surface of a water absorbent resin, by removing a volatile solvent, after adhering a liquid dissolved with or dispersed with an antimicrobial agent in the volatile solvent, onto the water absorbent resin. In JP-A-05 (1993)-179053 and JP-A-07 (1995)-165981, there is described a water absorbent resin containing a phosphate salt furnished with an antimicrobial property. In JP-A-11 (1999)-116829, there is described a water absorbent resin composition composed of a water absorbent resin, tannic acid (salt) and a composite silicate compound. In JP-A-09 (1997)-208787, there is described a water absorbent resin composition having a natural antimicrobial component extracted from a grape-fruit seed and/or herb included into or supported onto a water absorbent resin. In US-A-2003/0004479 and US-A-2004/0048955, there is described a particle-like water absorbent resin composition containing a plant powder and a surface-treated water absorbent resin, and having a malodor removing index of equal to or higher than 180. In US-A-2004-157989, there is described a water absorbent resin composition bound with cyclodextrin and/or a cyclodextrin derivative on a water absorbent resin by a covalent bond and/or an ionic bond. In WO01/41819, there is described a water absorbent resin composition composed of a water absorbent resin and a silver salt or colloidal silver.